In the last few years, significant advances have been made in management and control of wine-making, intended as the set of operations that contribute to the production of a wine through alcoholic fermentation of an initial liquid-solid mixture, must or pressed grapes.
For example, wine-making tanks have been conceived with automatic systems of pumping over and temperature control, with the possibility of heating or cooling, controlled with the aid of processing units that acquire data coming from several sensors arranged on board the tanks, able to detect, for example, the density of the must, the mass flow of the carbon dioxide (CO2) generated, the temperature of the must, etc. These systems enable the user to monitor the fermentation process and to manually adjust the wine-making parameters (including an increase and/or drop in temperature, the addition of nutrients, the operation of pumps and mechanical mixing actuators for the must, etc.).
In particular, in patent application WO 2011/058585, an automated wine-making system has been proposed that envisages processing, by means of a suitably trained neural network, a collection of historical data regarding past wine-making processes, stored methodically and systematically in a database, in order to obtain, by means of a data mining process, an optimal wine-making model, optimized for the characteristics and conditions peculiar to the wine-making process that is to be carried out. The system also envisages management and control of the wine-making process during its execution on the basis of the previously developed optimized model, by using a suitable artificial intelligence unit, in particular one implementing fuzzy logic algorithms, able to implement self-learning and adjustment operations referring to the optimized model in order to prevent/avoid/attempt to resolve possible anomalies of the fermentation kinetics, both automatically and by issuing alarms and work orders to operators. The same system envisages enlarging the above-mentioned database at the end of each wine-making process by using the information collected during execution of the same wine-making process and any other information considered useful (even if collected later on), so as to augment the content of the database in a continuous manner and consequently optimize the wine-making models, which will be subsequently developed starting from this database, being increasingly accurate and reliable.
The above-mentioned automated wine-making system also bases part of its operation, in particular regarding the control of the wine-making process as a function of the developed optimized model, on the data collected in the field by suitable sensors, including a fermentation mixture density sensor.
One problem that afflicts this system and, in general, solutions for automating the wine-making process that envisage real-time control of the fermentation mixture's conditions, is without doubt linked to the hostile conditions that arise inside the wine-making tanks during the course of fermentation.
It is well known that the raw material to be processed (pressed grapes) is a fluid mixture composed of many chemical components of both vegetable (sugars, acids, organic salts, etc.) and chemical (pesticides and fertilizers) origin, in which solid parts (of very variable size, ranging from specks of dust to parts of a few millimeters in size) are found in suspension, with adhesive properties (due to the sugars) and highly variable viscosity, which may reach very high values (up to having a gelatinous consistency). In general, it is known that this mixture may give rise to deposits due to the growth of salt crystals, as well as the growth of organic masses (moulds and bacterial colonies).
In this regard, Sablayrolles, J. M. “Control of alcoholic fermentation in winemaking: Current Situation and prospect”, Food Research International, 2009, although pointing out the advantages offered in principle by the real-time control of the fermentation process through use of suitable sensors (including, in particular, a density sensor for control of the fermentation curve or rate), underlines the fact that the technology available in the sensor field is generally found to be incompatible with the wine-making environment.
In particular, density sensors are known that exploit the buoyancy that acts on a movable float to detect the density of the fluid in which the float is at least partially immersed.
For example, patent application FR-A1-2 563 339 discloses a magnetic suspension densimeter in which the float is partially submerged in a liquid for which it is desired to measure the density and it is suitably kept in suspension by the action of an electromagnet and a position control loop.
However, density sensors using pressure sensors or exploiting the buoyancy that acts on a movable float (including magnetic suspension densimeters), or still are based on reflectometry, are heavily disturbed by the type of liquid to be measured; measurement becomes substantially unreliable if they are then left in contact with the liquid to be measured for long periods of time (days or weeks), as is instead required for real-time fermentation process monitoring applications.
For example, S. K. Singh “Industrial Instrumentation and Control”, McGraw Hill, 2008, page 253, considers magnetic suspension densimeters unsuitable for working in soiled and deposit-forming fluids.
Thus, the need is definitely felt, especially in the wine-making sector, for measuring instruments better suited to the hostile environments in which they are used, so as to allow effective implementation of the desired methods of process automation.